Biology: Your Brain In Love

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Now we were ready to gather our subjects, using word of mouth and the HAVE YOU JUST FALLEN MADLY IN LOVE? poster. Just and madly were the operative words. We sought only candidates who were so intensely in love that they could hardly eat or sleep, people whose romantic feelings were fresh, vivid, uncontrollable and passionate.

They were not difficult to find. Students immediately began to call Aron's psychology lab to volunteer. Mashek weeded out those who had metal in their heads (such as lip, tongue or nose jewelry or braces on their teeth) that would affect the magnet in the fMRI machine. She also excluded those who were claustrophobic, those taking medication that could affect brain physiology, and men and women who were left-handed. Brain organization can vary with handedness, and we needed to standardize our sample as much as possible.

At this point, I interviewed each candidate. My first question was always the same: "How long have you been in love?" My second question was the most important: "What percentage of the day and night do you think about your sweetheart?" Because obsessive thinking is a central ingredient of romantic passion, I sought only participants who thought about their beloved almost all their waking hours. I also looked for men and women who laughed and sighed more than usual during the interview.

If a potential subject showed signs of passion, I invited him or her to participate. We acquired two photographs: one of the beloved and one of an emotionally neutral individual. Generally the latter was someone the subject had known casually in high school or college. Then we set a date to put each subject into the brain scanner.

--THE BRAIN-SCANNING PROCEDURE

The procedure was simple but not easy. First Mashek and I made the participant as comfortable as possible in the scanner--a large, horizontal, cylindrical, cream-colored plastic tube that is open at both ends and extends from above the head to about the waist. After taking preliminary scans to establish basic brain anatomy, the 12-min. experiment started. First the subject looked at the photograph of the beloved on the screen for 30 sec. as the scanner recorded blood flow in various brain regions. Next the subject was shown a large number and asked to count backward for 40 sec. The participant then looked at the neutral photograph for 30 sec. while the brain was scanned again. Finally the subject was shown another large number and asked to count backward again, this time for 20 sec.

This cycle (or its reverse) was repeated six times--enabling us to collect 144 scans of different brain regions for each participant. After the experiment was over, I interviewed all the subjects again, asking how they felt and what they were thinking about during all parts of the test. To express our gratitude, we gave each participant $50 and a picture of his or her brain.

--THE BRAIN IN LOVE

Before we could understand the results of our scanning, we had to make an in-depth analysis of the brain pictures. The fMRI machine that we were using shows only blood-flow activity in specific brain regions rather than the chemicals involved. But because scientists know which kinds of nerves connect which kinds of brain regions, they can often surmise which brain chemicals are active when specific regions begin to glow.